I've found a workaround for this. that doesn't need GM
go outside your house, and stand on the tile adjacent to the tile inside you want the furniture on... hold right mouse button at your feet, then drag upward to make the tile the wall is on illuminate.
place the item there but without hitting done, press tab and walk back inside the house, then use the move controls to slide it through the wall an inside the house. position, click done.
job done